Heat treatment method and its apparatus

ABSTRACT

When the processed body holding member is moved upward or downward, the pressure in the reaction pipe and the shift and mount chamber is reduced down to several to several tens Torr, to reduce wind pressure applied to the processed body and thereby to suppress pressure fluctuations in the reaction pipe. Further, when the processed body holding member is moved upward or downward, the processing gas is passed in the same direction as the movement direction of the processed body holding member at a speed higher than the movement speed of the processed body holding member, to prevent the processing gas from being opposed to the processed body, so that the resistance received by the processed body is reduced and thereby the pressure fluctuations can be suppressed in the reaction pipe.

This application is a division of application Ser. No. 08/875,741 filedAug. 4, 1997, now U.S. Pat. No. 6,036,482, which is incorporated hereinin its entirety by reference which is a 371 of PCT/JP96/000279 filedFeb. 2, 1996.

TECHNICAL FIELD

The present invention relates to a heat treatment method and anapparatus.

BACKGROUND ART

As semiconductor device manufacturing methods, there are variousprocessing methods such as oxidizing processing for oxidizing a siliconsurface at a high temperature to obtain an oxide film (an insulatingfilm) on the silicon surface and, diffusing processing for heating asilicon layer formed with an impurity layer on the surface thereof tothermally diffuse the impurities in the silicon layer.

As the heat treatment apparatus used for oxidizing and diffusionprocessing, a vertical heat treatment apparatus of the batch type iswell known in the art. In this heat treatment apparatus, however, in thecase where an extremely thin film or a shallow position matching isrequired as when a capacitor insulating film or a gate oxide film isformed or when the diffusion processing is required for impurity ions,for instance, the film quality, the film thickness, and the diffusiondepth are all subjected to serious influence by the thermal budget(thermal history). In the batch type heat treatment apparatus, inparticular, there exists a large difference in thermal history betweenthe wafers first carried into a reaction pipe and the wafers carriedlast into the reaction pipe.

To overcome this problem, a single wafer type heat treatment apparatushas been so far studied, by improving a heat treating furnace of theabove-mentioned heat treatment apparatus. In this apparatus, after awafer has been mounted on a wafer holder member one by one and thencarried to a predetermined position in a reaction pipe, the carriedwafer is heated quickly. This single wafer type heat treatment apparatuswill be explained hereinbelow with reference to FIG. 18. In the drawing,a heat treating region of a vertical reaction pipe 1 is enclosed by aheat insulating body 10. In this reaction pipe, a supply pipe 11 and anexhaust pipe 12 are provided so that a processing gas can flow from theupper portion to the lower portion thereof.

In the reaction pipe 1, in order to secure the through-put, a waferholder member 13 is disposed so as to be movable up and down at a speedof about 150 to 200mm/sec, for instance. On the wafer holder member 13,a single wafer W is mounted by use of a wafer carrying member (notshown) disposed in a shift and mount chamber 14 disposed under thereaction pipe 1. Therefore, after having been moved upward to apredetermined position, the wafer W is heated to a predetermined heattreatment temperature by a heating section 15 composed of a resistanceheater 15 a and a heat uniformalizing body 15 b, and further oxidizedunder atmospheric pressure, for instance by supplying a processing gasinto the reaction pipe 1 through the processing gas supply pipe 11.

Further, a shutter 16 which functions as a light shutting valve ismovably disposed between the reaction pipe 1 and the shift and mountchamber 14 on the outer circumferential side of the shift and mountchamber 14, in order to cool the processed wafer W and to reduce theinfluence of the thermal history of the wafer W carried into the shiftand mount chamber 14. This is because the thermal history is caused bythe direct radiant heat radiated from the heating section 15. Further,the shutter 16 is formed with two semicircular cutout portions 16 a and16 b at each end thereof. These cutout portions 16 a and 16 b arebrought into tight contact with an outer circumference of a lift shaft17 of the wafer holder member 13 when closed. Further, a purge gassupply pipe (not shown) is disposed to purge a region communicating witha lower side (lower than the exhaust pipe 12) in the reaction pipe 1 byuse of a purge gas (e.g., inert gas).

In the prior art heat treatment apparatus as described above, however,when the wafer W is moved upward to a predetermined position from theshift and mount chamber 14 by use of the wafer holder member 13, thewafer W is moved upward in the reaction pipe 1 at a high speed of about150 to 200 mm/sec against the flow of the processing gas. Therefore,when the surface area of the wafer W is large, a large resistance (windpressure) is applied to the wafer W moving upward, so that a negativepressure is generated at the rearward (reverse surface side) region justunder the wafer W. As a result, a difference in pressure is generatedbetween the right surface side and the reverse surface side of thewafer.

Therefore, the gas stream is disturbed in the reaction pipe 1, andthereby the supply of the processing gas onto the wafer surface is notuniform. As a result, the uniformity of the intra-surface thickness ofthe film formed on the wafer W is degraded. For instance, when a targetintra-surface uniformity of the film thickness is 50±0.5 angstrom, thedifference in intra-surface thickness is as large as 50± severalangstrom (e.g., 5 angstrom). Here, the above-mentioned single wafer typeheat treatment apparatus has been developed in order to form anextremely thin film at a high precision so as to cope with themicrominiaturization technique for the semiconductor device. Therefore,the above-mentioned problem causes a serious problem in the heattreatment apparatus from the performance standpoint.

Further, in the case where a negative pressure is generated in theregion backward (the reverse side) of the wafer W as described above,when the wafer W is passed in front of the exhaust port, since the gasflows backward from the exhaust pipe 12 to the reaction pipe 1, thereexists another problem in that substances adhered onto the inner wall ofthe exhaust pipe 12 or particles collected by a particle removing devicedisposed in the exhaust pipe 12 flow in the backward direction into thereaction pipe 1, with the result that the reaction pipe 1 iscontaminated.

With these problems in mind, therefore, it is the object of the presentinvention to provide a heat treatment method and apparatus, which cansuppress the pressure fluctuations in the reaction pipe, when aprocessed body (e.g., substrate) is moved upward or downward, in orderto obtain a processed body (substrate) with a high intra-surfaceuniformity of film thickness.

DISCLOSURE OF THE INVENTION

The present invention is characterized in that, in a method ofheat-treating a processed substrate, while supplying a processing gas,by use of the apparatus having a reaction vessel enclosed by a heatingfurnace; a shift and mount chamber disposed on a lower side of thereaction vessel, for shifting and mounting the processed substrate; anda processed substrate holding member movable up and down between thereaction vessel and the shift and mount chamber, for holding theprocessed substrate, the method comprises a step of moving the processedsubstrate holding member upward or downward, while reducing pressurewithin the reaction vessel.

In the present invention, when the processed substrate is held by theprocessed substrate holding member and then moved upward or downward,the pressure in the reaction vessel is reduced down to an appropriatevalue. By doing this, the resistance received by the processed substratecan be reduced whenever the holder member is moved upward or downward.Therefore, since a difference in pressure between the right and reversesurfaces of the processed substrate can be reduced, it is possible tosuppress the pressure fluctuations in the reaction vessel. As a result,since the gas stream disturbance can be suppressed in the reactionvessel, a high intra-surface uniformity of the film thickness can beobtained on the processed substrate, and in addition the processedsubstrate is prevented from being contaminated by particles. Inaddition, in the present invention, since the shift and mount chamberand the reaction chamber are airtightly closed from each other; that is,since only the shift and mount chamber is opened to atmosphericpressure, it is possible to reduce the time required for pressure,reduction, thus increasing the throughput of the entire heat treatmentapparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal cross-sectional view showing a heat treatmentapparatus used for a first embodiment of the heat treatment methodaccording to the present invention;

FIG. 2 is a longitudinal cross-sectional view showing a heat treatmentapparatus used for a second embodiment of the heat treatment methodaccording to the present invention;

FIG. 3 is a longitudinal cross-sectional view showing a heat treatmentapparatus used for a third embodiment of the heat treatment methodaccording to the present invention;

FIG. 4 is an exploded view showing the opening/closing means (bellowsbody and shutter) used for the third embodiment shown in FIG. 3;

FIG. 5 is a longitudinal cross-sectional view showing a heat treatmentapparatus used for a fourth embodiment of the heat treatment methodaccording to the present invention;

FIG. 6 is a cross-sectional view of the heat treatment apparatus shownin FIG. 5, for assistance in explaining the processing gas flow from thelower portion to the upper portion in the reaction pipe;

FIG. 7 is a cross-sectional view showing the heat treatment apparatus ofFIG. 5, for assistance in explaining the processing gas flow from theupper portion to the lower portion in the reaction pipe;

FIG. 8 is a perspective view showing an embodiment of the wafer holdermeans provided with some thermo couples used for the heat treatmentapparatus according to the present invention;

FIG. 9 is a plane view showing the wafer holder means shown in FIG. 8;

FIG. 10 is a side view showing the wafer holder means shown in FIG. 8;

FIG. 11 is a perspective view showing another embodiment of the waferholder means provided with thermo couples;

FIG. 12 is a perspective view showing still another embodiment of thewafer holder means provided with thermo couples;

FIG. 13 is a side view showing still another embodiment of the waferholder means provided with thermo couples;

FIG. 14 is a longitudinal cross-sectional view showing a heat treatmentapparatus used for a sixth embodiment of the heat treatment methodaccording to the present invention;

FIG. 15 is a graphical representation showing a wafer lift speed patternaccording to the sixth embodiment of the heat treatment method shown inFIG. 14;

FIG. 16 is an illustration showing a gas flow near the exhaust port ofthe exhaust pipe in the sixth embodiment of the heat treatment methodshown in FIG. 14;

FIG. 17 is a diagrammatical construction view showing the heat treatmentapparatus used for a seventh embodiment of the heat treatment methodaccording to the present invention; and

FIG. 18 is a longitudinal cross-sectional view showing a prior art heattreatment apparatus.

BEST EMBODIMENTS FOR REALIZING THE INVENTION First Embodiment

FIG. 1 is a longitudinal cross-sectional view showing the firstembodiment of the heat treatment method according to the presentinvention. In FIG. 1, a reference numeral 2 denotes a reaction pipe (ora reaction vessel) of a double pipe structure composed of an outer pipe2 a and an inner pipe 2 b. The outer pipe 2 a is formed of quartz forinstance and opened at the lower end and closed at the upper end. Theinner pipe 2 b is also formed of quartz and disposed in the outer pipe 2a. Further, an opening portion 20 is formed at the top center of theinner pipe 2 b as a processing gas supply passage or port.

The reaction pipe 2 b is disposed at the center of a heating furnace200. The heating furnace 200 is provided with a heat uniformalizingmember 21 formed of silicon carbide (SiC), for instance and disposed soas to cover the upper surface and the periphery of the reaction pipe 1with a predetermined gap relative therebetween. Further, an outer body23 provided with a heat insulating body 22 and a water cooled jacket 23a is disposed outside the heat uniformalizing member 21. Further, aheating source 24 constructed by a resistance heating body is arrangedbetween the upper surface of the heat uniformalizing member 21 and theheat insulating body 22.

One end of each of two processing gas supply pipes 3 a and 3 b isconnected to the lower portion of the reaction pipe 2, and opened to agap formed between the outer pipe 2 a and the inner pipe 2 b. On theother hand, the other end of each of the two processing gas supply pipes3 a and 3 b is connected to a processing gas source (not shown).

On the lower side of the reaction pipe 2, a cylindrical body 4 having awater cooled jacket is disposed. The cylindrical body 4 has an upper endportion airtightly connected to the lower end portion of the reactionpipe 2 and an inner space communicating with the space formed in thereaction pipe 2.

One end of each of two exhaust pipes 5 a and 5 b having an innerdiameter of 25 mm, for instance is connected to the upper side surfaceof the cylindrical body 4 in such a way as to be opposed to each otherin the radial direction thereof. The exhaust pipe 5 a is branched midwayinto two exhaust pipes 51 and 52. The other end of one exhaust pipe 51is connected to a pressure reduction means (e.g., vacuum pump) 54 via ashut-off valve V1 and a pressure adjusting valve 53, and the other endof the other exhaust pipe 52 is connected to an exhaust pump 56 via ashut-off valve V2 and a pressure adjusting valve 55. Here, the otherexhaust pipe 5 b is the same in construction as that of the exhaust pipe5 a, and therefore not shown in FIG. 1.

On the lower side from the exhaust ports of the two exhaust pipes 5 aand 5 b disposed on the cylindrical body 4 is a shift and mount chamber41 for shifting a wafer W from an outside of the heat treatmentapparatus to wafer holder means (described later) and mounting the waferW on the same wafer holder means. A carry port 42 for carrying a wafer Win and out therethrough is formed in the side wall portion of the shiftand mount chamber 41. The carry port 42 is opened or closed by a gatevalve. Further, a shutter having two shutter blades S1 and S2 (an openstate is shown in FIG. 1) for shutting off radiant heat generated by thereaction pipe (or vessel) 2 is disposed around the upper portion of theshift and mount chamber 41. Further, another shutter having two shutterblades S3 and S4 for shutting off the bottom portion of the cylindricalbody 4 is also disposed around the lower portion of the shift and mountchamber 41. Further, the shutter S3, S4 is formed with a semicircularcutout portion for an inner end of each of two shutter blades, so as toenclose a lift shaft 63 when closed, (the two shutter blades are closedin FIG. 1). Further, the reference numerals 43, 44, 45 and 46 are allstand-by chambers of the two shutters S1, S2 and S3, S4. Further, purgegas supply pipes G1 to G4 are connected to the bottom portions of theseshutter stand-by chambers 43 to 46, respectively, and a purge gas supplypipe G5 is connected to the bottom portion of the cylindrical body 4.

The wafer holder means (or a processed substrate holding member) 6 forholding a processed substrate is disposed in the reaction pipe 2. Thewafer holder means 6 is so constructed as to hold a wafer W onprojecting portions 62 projecting from a mount portion 61. The waferholder means 6 is provided with three pressure detecting portions P1 toP3. Three detection ends (top ends) of these pressure detecting portionsP1 to P3 are located at a position slightly over a roughly centralportion of the right surface of the wafer W, at a position slightlyradially outward away from a circumferential portion of the wafer W, andat a position slightly under a roughly central portion of the reversesurface of the wafer W, respectively. These pressure detecting portionsP1 to P3 are of the suction type, for instance, and a base end side ofeach suction pipe is connected to a detection unit (not shown) beingguided through the lift shaft 63 and being taken out of the lower end ofthe lift shaft 63.

The wafer holder means 6 is mounted on top of the lift shaft 63. Thelift shaft 63 is moved upward and downward by a lift mechanism 64 suchas a ball screw disposed at the lower end portion of the cylindricalbody 4. The lift shaft 63 is provided with an inner shaft driven by amotor M to rotate the wafer holder means 6.

The function of the first embodiment as described above will bedescribed hereinbelow. First, the wafer holder means 6 is positioned inthe shift and mount chamber 41 as shown by dashed lines in FIG. 1. Then,a gate valve (not shown) is opened to carry a wafer W (i.e., a processedsubstrate) through the carry port 42, and further mounted on the waferholder means 6. On the other hand, here, since radiant heat isintroduced from the heating source 24 into the reaction pipe 2 throughthe heat uniformalizing body 21, a uniform-heat region at apredetermined temperature can be formed in the reaction pipe 2. Further,two processing gases (e.g., a mixture gas of O₂ and HCL) are suppliedfrom the gas supply pipes 3 a and 3 b into the reaction pipe 2 throughthe top opening portion 20 of the inner pipe 2 b. The flow rates of thetwo processing gases flowing through the opening portion 20 of the innerpipe 2 b are 6.0 liter/min in O₂ and 0.25 liter/min in HCL, forinstance, respectively. Under these conditions, the shutter S1, S2(shown by the dot-dot-dashed lines) and the shutter S3, S4 (shown by thesolid lines) are all closed as shown in FIG. 1, so that the radiant heatfrom the reaction pipe 2 can be shut off by the shutter S1, S2 (shown bythe dot-dot dashed lines).

Successively, after the shutter S1, S2 has been opened, the wafer holdermeans 6 is moved upward. At this time, the valve V1 is opened and thevalve V2 is closed, so that immediately before the wafer holder means 6is moved upward, the inner pressure of the reaction pipe 2 and the shiftand mount chamber 41 is reduced down to several to several tens of Torrby the vacuum pump 54 through the exhaust pipes 51 and 5 a. Here, thepressure in the reaction pipe 2 and the shift and mount chamber 41 isdecided according to the processing conditions. Under certain processingconditions, when the wafer holder means 6 is being moved upward, thepressure on the reverse surface side of the wafer W and that on theright surface side of the wafer W are both detected by the pressuredetecting portions P1 to P3, to obtain a pressure difference between theright and reverse surfaces of the wafer W in correspondence to themovement speed of the wafer holder means 6. In this case, for instance,the pressure is so decided that the obtained pressure difference can bereduced below a predetermined value. Here, if the pressure in thereaction pipe 2 is reduced excessively, since the time required forpressure reduction and the time required for pressure restoration to theatmospheric pressure are both lengthened, the total throughput decreasesaccordingly. Therefore, here, an appropriate pressure value is decidedto such a value that the disturbance of the gas stream can besufficiently prevented at a set wafer movement speed. Further, thepressure within the reaction pipe 2 can be controlled by adjusting theopening rate of the pressure adjusting valve 53, for instance.

After the wafer holder means 6 has been moved upward to a predeterminedposition in the reaction pipe 2, or when the wafer holder means 6 hasreached a position slightly before the heat processing region, thepressure in the reaction pipe 2 is raised up to near the atmosphericpressure by adjusting the opening rate of the pressure adjusting valve53. After that, the valve 53 is closed and the valve V2 is opened toswitch the exhaust from the vacuum pump 54 to the exhaust pump 56.Therefore, the inner pressure of the reaction pipe 2 and the shift andmount chamber 41 is set to the atmospheric pressure. Further, the waferW is heated up to 1000° C., for instance, to form an oxide film with afilm thickness of 50 angstrom on the wafer W.

After that, the valve V2 is closed and the valve V1 is opened, to reducethe inner pressure of the reaction pipe 2 and the shift and mountchamber 41 to several to several tens of Torr by use of the vacuum pump54 Under these conditions, the wafer holder means 6 is moved downward tothe shift and mount chamber 41. Further, the valve Vi is closed and thevalve V2 is opened to return the pressure in the reaction pipe 2 and theshift and mount chamber 41 to the atmospheric pressure. After that, theshutter S1, S2 is shut off to dismount the wafer W from the wafer holdermeans 6.

As described above, in the first embodiment, when the wafer holder means6 is being moved upward, since the pressure in the reaction pipe 2 andthe shift and mount chamber 41 is reduced to a predetermined pressure,it is possible to minimize the resistance (wind pressure) applied to thewafer W when the wafer W is being moved. That is, although a negativepressure can be generated on the reverse surface side of the wafer Wwhen the wafer W is moved upward, or on the right surface side of thewafer W when the wafer W is moved downward, since the negative pressureis small, it is possible to minimize the pressure difference between theright and reverse surface sides of the wafer W. Therefore, it ispossible to suppress the pressure fluctuations in the reaction pipe 2,with the result that the disturbance of the gas stream can besuppressed.

As a result, since the processing gas can flow uniformly along thesurface of the wafer W, the growth of the oxide film will not bedisturbed and thereby the film thickness of the oxide film can becontrolled at a high precision, so that a high intra-surface uniformityof oxide film can be obtained. Further, as described above, since thenegative pressure can be reduced on the right and reverse surface sidesof the wafer W during the upward or downward movement of the wafer W,when the wafer W is passed through the area near the exhaust ports,backward flow does not occur at all in the exhaust pipes 5 a and 5 b, orelse if it occurs, the backward flow is extremely small.

As a result, since substances adhered in the exhaust pipes 5 a and 5 bor particles in the particle removing device will not or almost do notflow backward into the reaction pipe 2, it is possible to prevent theinside of the reaction pipe 2 from being contaminated.

Further, when a wafer W is processed for oxidization under differentprocessing conditions in accordance with the above-mentioned method, thepressure difference between the right and reverse surfaces of the waferW according to the movement speed of the wafer holder means 6 can bedetected by the pressure detecting portions. Further, on the basis ofthese detected values, appropriate pressure conditions can be set, andthe inner pressure of the reaction pipe 2 is reduced on the basis of thepressure conditions thus determined whenever the wafer W is being movedupward or downward

Second Embodiment

The second embodiment of the heat treatment method according to thepresent invention will be described hereinbelow with reference to FIG.2. In this second embodiment, pressure detecting means 60 composed of aplurality of pressure detecting portions P1 to Pn are arranged in avertical direction along the inner surface of the inner pipe 2 b of thereaction pipe 2, for instance. An appropriate pressure in the reactionpipe 2 and the shift and mount chamber 41 can be obtained on the basisof the detected pressure values of these pressure detecting portions P1to Pn, when the wafer holder means 6 is moved upward and downward. Inmore detail, when the wafer holder means 6 is being moved upward, thepressure in the reaction pipe 2 is detected by use of the pressuredetecting portions P1 to Pn, so that the pressure distribution in thereaction pipe 2 according to the upward movement of the wafer W can beobtained on the basis of the relationship between the wafer positionsand the pressure detection values. When the pressure distribution can beonce obtained for each condition by changing the pressure reductionconditions, an appropriate pressure value in the reaction pipe 2 can bedecided in such a way that the obtained pressure distribution can beuniformalized. Further, when the wafer holder means 6 is moved downward,an appropriate pressure value in the reaction pipe 2 can be decided inthe same way. Further, this second embodiment is the same inconstruction as the first embodiment, for the portions related to thepressure detecting means.

In the second embodiment as described above, the pressure distributioncorresponding to the moving speed of the wafer holder means 6 movedupward or downward is previously examined by use of the pressuredetecting portions P1 to Pn, and then an appropriate pressure value inthe reaction pipe 2 is decided in such a way that the obtained pressuredistribution can be uniformalized. As a result, the pressurefluctuations in the reaction pipe 2 when the wafer holder means 6 ismoved upward and downward can be suppressed, with the result that it ispossible to form an oxide film on the wafer W at a high precision with ahigh intra-surface uniformity of the film thickness and further toprevent particles from being mixed, in the same way as with the case ofthe first embodiment.

Third Embodiment

The third embodiment of the heat treatment method according to thepresent invention will be described hereinbelow with reference to FIGS.3 and 4. In this third embodiment, opening and closing means (shutter) 7for shutting the radiant heat generated by the heating source 24 andfurther for closing the space between the reaction pipe 2 and the shiftand mount chamber 41 airtightly is disposed between the reaction pipe 2and the shift and mount chamber 41. In addition, a pressure reducingexhaust pipe 8 is connected to the shift and mount chamber 41.

Here, the opening and closing means 7 comprises a shutter S1, S2 asshown in FIGS. 2 and 3 and a ring-shaped bellows body 71 disposed on theupper inner walls of the two stand-by chambers 43 and 44 and urged tothe circumferential upper surface of the two shutter blades S1 and S2.Therefore, when the shutter S1, S2 is closed, the lower surface of theurging portion of the bellows body 71 is brought into tight contact witha push region 70 (shown in FIG.4) of the shutter blades S1 and 52, sothat it is possible to partition the space airtightly between thereaction pipe 2 and the shift and mount chamber 41. The bellows body 71is so constructed as to be extended and retracted (movable up and down)by controlling the inner pressure thereof. Further, the exhaust pipe 8is connected to a vacuum pump 82 via a shutting valve V3 and a pressureadjusting valve 81. Further, in this third embodiment, the constructionother than the above is substantially the same as with the case of thefirst embodiment shown in FIG. 1.

In this third embodiment, first both the shutters (S1, S2) and (S3, S4)are closed. Under these conditions, a wafer W is carried into the shiftand mount chamber 41 through the carry port 42 by opening the gate valveand further mounted on the wafer holder means 6 disposed in the shiftand mount chamber 41. In this case, since the bellows body 71 is urgedagainst the upper surface of the shutter S1, S2 and further the shutterS1, S2 is closed airtightly, the reaction pipe 2 and the shift and mountchamber 41 can be partitioned airtightly. Further, the pressure of thereaction pipe 2 is reduced to a predetermined pressure reductioncondition (atmosphere) via the exhaust pipe 51 in the preceding process.

After that, the pressure of the shift and mount chamber 41 is reduceddown to a predetermined pressure by the vacuum pump 82 and through theexhaust pipe 8. After the valve V3 has been closed, the shutter S1, S2is opened. Under these conditions, the wafer holder means 6 is movedupward to a predetermined position in the reaction pipe 2. When thewafer W is being moved upward, the reaction pipe 2 is pressure reducedand further exhausted by the vacuum pump 54 through the two exhaustpipes 5 a and 5 b down to a pressure reduction atmosphere, whilesupplying the processing gas and the purge gas in each predeterminedflow rate, through the opening portion 20 of the reaction pipe 2 andthrough the purge gas supply pipes G1 to G5, respectively. Slightlybefore or immediately when the wafer W reaches the heat processingregion, the flow rates of both the processing gas and the purge gas areincreased, and further the pressure in the reaction pipe 2 is increasedto near the atmospheric pressure by adjusting the opening rate of thepressure adjusting valve 53. After that, the valve V1 is closed and thevalve V2 is opened, to heat-treat the surface of the wafer W or to forman oxide film on the wafer surface under the atmospheric pressure, whileexhausting the reaction pipe 2 by use of the exhaust pump 56.

Successively, the valve V2 is closed and the valve V1 is opened toreduce the pressure in the reaction pipe 2 and the shift and mountchamber 41 down to a predetermined pressure by the vacuum pump 54. Underthese pressure reduction conditions, the wafer holder means 6 is moveddownward into the shift and mount chamber 41. Further, the shutter S1,S2 is closed and then the bellows body 7 is extended to close the spaceairtightly between the reaction pipe 2 and the shift and mount chamber41. After that, the purge gas is supplied, and the pressure of the shiftand mount chamber 41 is returned to the atmospheric pressure. Further,the carry port (valve gate) 42 is opened to exchange the wafer W with anew one.

In this third embodiment, the same effect as with the case of the firstembodiment can be obtained. In addition, since the pressure-reducingexhaust pipe 8 is further connected to the shift and mount chamber 41and further since the reaction pipe 2 and the shift and mount chamber 41can be airtightly closed from each other by use of both the shutter S1,S2 and the bellows body 7, it is possible to maintain the reaction pipe2 in a pressure reduction atmosphere, whenever the wafer W is beingmounted on the wafer holder means 6 in the shift and mount chamber 41.After the wafer has been mounted on the wafer holder means 6, since onlypressure of the shift and mount chamber 41 is reduced, the space whosepressure must be reduced is small, as compared with when the pressure ofboth the reaction pipe 2 and the shift and mount chamber 41 is bothreduced, with the result that the throughput of the heat treatmentapparatus can be improved as a whole.

Fourth Embodiment

The fourth embodiment of the heat treatment method according to thepresent invention will be described hereinbelow with reference to FIG.5. In this fourth embodiment, one end of each of the two processing gassupply pipes 9 a and 9 b is connected to the lower portion of thereaction pipe 2 to supply a processing gas into the inside of the innerpipe 2 b, and further one end of an exhaust pipe 91 is connected to theouter pipe 2 a to exhaust the processing gas from a space between theouter pipe 2 a and the inner pipe 2 b of the reaction pipe 2. Thisexhaust pipe 91 is connected to the exhausting means (not shown) via avalve V6. The fourth embodiment is the same in construction as the firstembodiment shown in FIG. 1, except the above-mentioned point and thearrangement of the pressure-reducing means. Further, as the pressuredetecting means, the same means as shown in FIG. 2 can be used. Further,the construction as shown in FIG. 3 can be used as the constructionother than the above-mentioned points.

In this fourth embodiment, the wafer W is mounted on the wafer holdermeans 6 in the shift and mount chamber 41. At the same time, the valvesV4 and V5 of the exhaust pipes 5 a and 5 b are both closed, and thevalve V6 of the exhaust pipe 91 is opened. Further, when the reactionpipe 2 is being exhausted through the exhaust pipe 91, the processinggas is supplied to the reaction pipe 2 through the processing gas supplypipes 9 a and 9 b, to pass the processing gas from the lower portion tothe upper portion of the reaction pipe 2 at a speed higher than theupward moving speed of the wafer holder means 6, for instance as shownin FIG. 6.

After that, the shutter S1, S2 is opened to move the wafer holder means6 upward to a predetermined position in the reaction pipe 6, foroxidization processing of the wafer W. When the wafer W is being movedupward, the purge gas is stopped from being supplied through the purgegas supply pipes G1 to G5. Upon end of this processing, the valve V6 isclosed to stop the exhaust through the exhaust pipe 91 and the gassupply through the processing gas supply pipes 9 a and 9 b, and furtherthe valves V4 and V5 are both opened to exhaust the reaction pipe 2through the exhaust pipes 5 a and 5 b. At the same time, the processinggas is supplied through the processing gas supply pipes 3 a and 3 b (3 bis not seen in FIGS. 6 and 7), to pass the processing gas from the upperportion to the lower portion of the reaction pipe 2 at a speed higherthan the downward moving speed of the wafer holder means 6, for instanceas shown in FIG. 7.

In the fourth embodiment, when the wafer holder means 6 is being movedupward or downward, since the processing gas is passed in the samedirection as that of the wafer holder means 6 at a speed higher than themovement speed of the wafer holder means 6, as compared with when thewafer W is moved in a direction opposite to that of the processing gasflow, the resistance of the wafer W against the processing gas isreduced, so that the wind pressure applied to the wafer W can beextremely reduced. As a result, it is possible to suppress the pressurefluctuations in the reaction pipe 2 when the wafer holder means 6 isbeing moved, with the result that an oxide film can be formed on thewafer W at a high precision with a high intra-surface uniformity of thefilm thickness and further to prevent particles from being mixed, in thesame way as with the case of the first embodiment.

Further, in this fourth embodiment, it is also preferable to reduce thepressure in the reaction pipe 2 when the wafer holder means 6 is beingmoved upward and downward. In this case, since the wind pressure appliedto the wafer W can be further reduced, it is possible to form an oxidefilm on the wafer W at a high precision with a high intra-surfaceuniformity of the film thickness.

Further, when the wafer holder means 6 is moved upward and downward, itis also preferable to control the pressure in the reaction pipe bydetecting the pressure by use of the pressure detecting portions and bycontrolling the opening rate of the valves on the basis of the detectedpressure values by use of a control section.

Fifth Embodiment

In this fifth embodiment, the temperature of the wafer W is detected ata plurality of different points, in order to decide a speed pattern inaccordance with which the speed of the wafer holder means 6 is moved toa predetermined position in the heat treatment region, a timing at whichthe wafer holder means 6 is moved downward from the heat treatmentregion, or a timing at which an oxidizing gas is switched to an inertgas or vice versa in the reaction pipe 2, for each process. For thispurpose, it is possible to provide a plurality of temperature detectingdevices such as thermo couples for the wafer holder means 6.

By the way, when a plurality of thermo couples are provided for thewafer holder means 6, it is necessary to consider such a constructionthat the wafer temperatures can be detected at a plurality of pointswithout interference between the thermo couples and the carry arms forexchanging the wafer W with a new one. A practical wafer holder means 6having the thermo couples of the construction as described above will bedescribed hereinbelow.

In the examples as shown in FIGS. 8 to 11, a protective tube (e.g.,formed of quartz) is inserted into a support shaft 30 (including thelift shaft and the rotary shaft in the afore-mentioned embodiments) ofthe wafer holder means 6. Further, wires of a plurality (e.g., six)thermo couples are passed through the protective tube. Further, each endof these wires of the thermo couples are taken out from the protectivetube and then bent as shown in FIG. 8. In more detail, three thermocouples 92 a to 92 c are arranged in such a way as to extend from thereverse surface to the right surface of the wafer W and further thecross-sectional shape thereof can be seen as a horizontal U-shape whenseen from the side. Further, when seen from above (in the planeposition), these three thermo couples 92 a to 92 c are arrangedextending in the wafer radial direction and being shifted 45 degrees and45 degrees with respect to the center of the wafer W. Further, the threeends of the three thermo couples 92 a to 92 c are located at a positionnear an intermediate portion between a center and an outer edge of thewafer W, at a position near the center of the wafer W, and at a positionnear the outer edge of the wafer W, respectively.

Further, the three ends of the remaining three thermo couples 92 d to 92f are located at a position near the outer edge of the wafer W and belowa distance (through which the carry arm 31 can be inserted) downwardaway from the reverse surface of the wafer W, at a position near theintermediate portion between the center and the outer edge of the waferW and below the same distance downward away as above, and a position ofthe center of the wafer W below the reverse surface of the wafer W. Thetwo thermo couples 92 d and 92 e are located at an opposite positionrelative to the thermo couples 92 c and 92 a with respect to the centerof the wafer W. These thermo couples can be formed by inserting thermocouple wires each having a wire diameter of about 0.5 mm into the quartzinner tube having an outer diameter of about 4 mm, and further byfitting a quartz outer tube closed at a top thereof and having adiameter of 5 mm to the inner tube. Further, in FIG. 10, a referencenumeral 32 denotes a holder body, and 33 denotes projecting portions forsupporting the wafer W. However, these portions are not shown in FIGS. 8and 9.

In the wafer holder means 6 as shown in FIG. 8, the wafer W can beexchanged by holding the wafer W; that is, by inserting the carry arm 31from between the two thermo couples 92 d and 92 e to between the endportions of the three thermo couples 92 d, 92 e and 92 f and the reversesurface of the wafer W. Therefore, it is possible to prevent theinterference between the carry arm 31 and the thermo couples 92 a to 92f.

Further, as shown in FIG. 11, it is possible to arrange three thermocouples 93 a to 93 c for detecting the right surface side of the wafer Wby shifting 90 degrees and 90 degrees with respect to the center of thewafer W, in such a way that the carry arm 31 can be inserted from thereverse surface side of the water W (where the thermo couples 93 a to 93c are not arranged) into between the reverse surface of the wafer W andthe central thermo couple 93 d. Or else, as shown in FIG. 12, when thewafer holder means 6 as shown in FIG. 8 is used, a carry arm 31 formedwith a cutout portion 34 at an end thereof is inserted from the side ofthe thermo couple 92 e arranged on the reverse surface of the wafer W insuch a way that the two thermo couples 92 e and 92 f can be insertedinto the cutout portion 34 of the carry arm 31 for prevention ofinterference between the carry arm 31 and the thermo couples 92 e and 92f.

Further, it is possible to adopt such a construction that the thermocouples themselves can hold the wafer in such a way that the thermocouples have two functions for holding the wafer W and for detecting thewafer temperature. FIG. 13 is an example of this construction, in whichthere are provided some thermo couples 94 for holding the reversesurface of the wafer W at the circumferential edge thereof, some thermocouples 95 for detecting the temperatures of the outer circumferentialedges of the wafer W, and a thermo couple 96 for detecting thetemperature at the central portion of the reverse surface of the waferW. In this case, the carry arm is inserted into a gap between the waferW and the thermo couple 96. Further, as the some thermo couples 94 and95, three thermo couples 94 and 95, for instance are each arranged beingshifted 120 degrees and 120 degrees in the wafer circumferentialdirection and with respect to the center of the wafer W.

Sixth Embodiment

FIG. 14 is a longitudinal cross-sectional view showing the sixthembodiment of the heat treatment method according to the presentinvention. In FIG. 14, a reference numeral 2 denotes a reaction pipe ofdouble pipe structure composed of an outer pipe 2 a and an inner pipe 2b. The outer pipe 2 a is formed of quartz for instance and opened at thelower end and closed at the upper end. The inner pipe 2 b is also formedof quartz and disposed within the outer pipe 2 a. Further, an openingportion 20 is formed at the top center of the inner pipe 2 b as aprocessing gas supply passage or port.

A heat uniformalizing member 21 formed of silicon carbide (SiC), forinstance is disposed so as to cover the upper surface and the peripheryof the reaction pipe 1 with a predetermined gap. Further, an outer body23 provided with a heat insulating body 22 and a water cooled jacket 23a is disposed on the outside of the heat uniformalizing member 21.Further, a heating source 24 constructed by a resistance heating body isarranged between the upper surface of the heat uniformalizing member 21and the heat insulating body 22. In this sixth embodiment, the heatingfurnace of the heat treatment apparatus is composed of the heatuniformalizing member 21, the heat insulating body 22, and a heatingsource 24. Here, however, a heat radiating lump can be used instead ofthe heating source.

One end of each of two processing gas supply pipes 3 a and 3 b isconnected to the lower portion of the reaction pipe 2 in such a way asto be opened to a gap formed between the outer pipe 2 a and the innerpipe 2 b, and the other end of each of the two processing gas supplypipes 3 a and 3 b is connected to a processing gas source (not shown).

On the lower side of the reaction pipe 2, a cylindrical body 4 having awater cooled jacket is disposed. The cylindrical body 4 has an upper endportion airtightly connected to the lower end portion of the reactionpipe 2 and an inner space communicating with the space formed in thereaction pipe 2.

One end of each of two exhaust pipes 5 a and 5 b having an innerdiameter of 25 mm, for instance is connected to the upper side surfaceof the cylindrical body 4 in such a way as to be opposed to each otherin the radial direction thereof. The other end of each of these exhaustpipes 5 a and 5 b is connected to each of two exhaust pumps 50 a and 50b each provided with an auto-pump controller (referred to as APC).

On the lower side from the exhaust ports of the two exhaust pipes 5 aand 5 b disposed on the cylindrical body 4, a shift and mount chamber 41for shifting a wafer W from the outside of the heat treatment apparatusto the wafer holder means (described later) 25 and further mounting theshifted wafer W on the wafer holder means 25 is formed. A carry port 42for carrying a wafer W in and out there-through is formed on the sidewall portion of the shift and mount chamber 41. The carry port 42 isopened or closed by a gate valve. Further, a shutter having two bladesS1 and S2 for shutting off radiant heat generated from the side of thereaction pipe 2 is disposed on the upper sides of the shift and mountchamber 41. Further, another shutter having two blades S3 and S4 forshutting off the bottom portion of the cylindrical body 4 is disposed onthe lower sides of the shift and mount chamber 41. Further, each of thetwo shutter blades S3 and S4 is formed with a semicircular cutoutportion for enclosing a lift shaft 26 airtightly at an end thereof whenclosed. Further, the reference numerals 43, 44, 45 and 46 are stand-bychambers of these shutters (S1, S2) and (S3, S4). Further, purge gassupply pipes 6 a, 6 b, 7 a and 7 b for purging an inert gas, forinstance are connected to the bottom portions of the shutter stand-bychambers 43, 44, 45 and 46, respectively. Further, a purge gas supplypipe 8 is connected to the bottom portion of the cylindrical body 4.

The wafer holder means 25 for holding a processed substrate is disposedin the reaction pipe 2. The wafer holder means 25 is mounted on top ofthe lift shaft 26. The lift shaft 26 is moved upward and downward by alift mechanism 27 such as a ball screw disposed at the lower end portionof the cylindrical body 4. The lift mechanism 27 is controlled by aspeed control section 28, so that the movement speed of the wafer holdermeans 25 can be controlled. The lift shaft 26 is formed with an innershaft driven by a motor M to rotate the wafer holder means 25.

The function of the sixth embodiment as described above will bedescribed hereinbelow. First, the wafer holder means 25 is positioned onthe lower side of the shift and mount chamber 41, as shown by thedot-dot-dashed lines in FIG. 14. Then, a gate valve is opened to carry awafer W (i.e., a processed substrate) through the carry port 42, andfurther mounted on the wafer holder means 25.

On the other hand, here, since radiant heat is introduced from theheating source 24 into the reaction pipe 2 through the heatuniformalizing body 21, a uniform-heat region of a predeterminedtemperature can be formed in the reaction pipe 2. Further, twoprocessing gases (e.g., a mixture gas of O₂ and HCL) are supplied fromthe gas supply pipes 3 a and 3 b into the reaction pipe 2 through thetop opening portion 20 of the inner pipe 2 b. The flow rates of the twoprocessing gases flowing through the opening portion 20 are 6.0liter/min in O₂ and 0.25 liter/min in HCL, for instance, respectively.Under these conditions, the two shutters S1, S2 and S3, S4 are bothclosed as shown in FIG. 14, so that the radiant heat from the reactionpipe 2 can be shut off by the shutter S1, S2.

Further, a purge gas (e.g., N₂ gas) is supplied into the cylindricalbody 4 through the purge gas supply pipes 6 a, 6 b, 7 a, 7 b and 8, allconnected to the cylindrical body 4, at a flow rate of 5 liter/min intotal. Further, the processing gas and the purge gas are both exhaustedthrough the exhaust pipes 5 a and 5 b, respectively. By doing this, theupper region above the exhaust pipes 5 a and 5 b becomes a processinggas atmosphere under atmospheric pressure. Further, the lower regionbelow the exhaust pipes 5 a and 5 b becomes the purge gas atmosphere.Further, after the two shutters S1, S2 and S3, S4 have been opened, thewafer holder means 25 is moved upward.

The wafer holder means 25 is moved upward under control of the controlsection 28 on the basis of a speed pattern as shown in FIG. 15. In moredetail, first the wafer holder means 25 is moved upward from the shiftand mount chamber 4 to a region D including a height the same as orroughly the same as that of the exhaust pipes 5 a and 5 b at a firstspeed (e.g., 150 to 200 mm/sec). In the region D, the movement speed ofthe wafer holder means 25 is decelerated to a second speed (e.g., 10 to50 mm/sec) lower than the first speed, to such an extent that theprocessing gas will not flow backward by a negative pressure generatedon the reverse surface side of the wafer W when the wafer W is passed.Further, after the wafer holder means 25 has passed through the heightregion D, the wafer holder means 25 is moved upward at a third speedhigher than the second speed (e.g., the same speed as the first speed),until the wafer W reaches a predetermined position. At this position,the wafer W is heated up to 1000° C., for instance, to form an oxidefilm having a film thickness of 50 angstrom, for instance. After that,the wafer holder means 25 is moved downward to the shift and mountchamber 4 on the basis of the speed pattern opposite to that used whenmoved upward. Further, the shutters S1, S2 and S3, S4 are both closed,to exchange the wafer W with a new one through the carry outlet port 42.

As described above, in the sixth embodiment, since the wafer holdermeans 25 is decelerated when the wafer W is passed through the heightregion D the same as or roughly the same height as that of the exhaustpipes, although a negative pressure is generated on the reverse surfaceside of the wafer W when the wafer holder means 25 is moved upward or onthe right side surface side thereof when moved downward, the generatednegative pressure is sufficiently small. Therefore, as shown in FIG. 16,the stream of the processing gas and the purge gas directed toward thenegative pressure region formed after the wafer W has been passed can bereduced, so that the gas near the exhaust ports flows smoothly towardthe exhaust ports. Therefore, the exhaust gas will not or almost doesnot flow backward in the exhaust pipes 5 a and 5 b; in other words, evenif the backward flow occurs, the degree thereof is extremely small.

As a result, substances adhered onto the exhaust pipes 5 a and 5 b orparticles in the particle removing device will not or almost does notflow backward, so that the contamination of the reaction pipe 2 can beprevented. Further, in case the backward flow occurs in the exhaustpipes 5 a and 5 b, the gas flow is disturbed, so that the purge gas ismixed with the processing gas over the height region D of the exhaustpipes 5 a and 5 b. In this case, since the processed gas is diluted,when the wafer W enters the processing gas atmosphere, there exists aproblem in that when the wafer W enters the processing gas atmosphere,the growth of the oxide film is disturbed on the surface of the wafer W.In this sixth embodiment, however, since the particles within theprocessing gas atmosphere are suppressed and since the disturbance ofthe oxide film growth can be reduced, it is possible to control the filmthickness of the oxide film at a high precision, with the result that ahigh intra-surface uniformity of the film thickness can be obtained andthereby the yield of the products can be improved.

Here, the height region D in which the wafer W is moved at a lower speed(e.g., the second speed) is a range between a position about 10 cmupward way from the upper end of the exhaust ports and a position about10 cm downward way from the lower end of the exhaust ports. In otherwords, since the wafer holder means 25 is moved at a higher speed onboth upper and lower sides of this height region D and at a lower speedonly within this height region D, the influence upon the throughput isnot large. Further, in FIG. 15, when the wafer holder means 25 isstarted to move or stopped from moving, although there exist anacceleration zone and a deceleration zone strictly on both the upper andlower sides of this height region D, since the speed change can beattained momentarily, the above-mentioned acceleration and decelerationspeed zones are not expressed in FIG. 15.

Seventh Embodiment

The seventh embodiment of the heat treatment method according to thepresent invention will be described hereinbelow with reference to FIG.17. In this seventh embodiment, pressure adjusting valves V1 to V9 areprovided for the processing gas supply pipes 3 a and 3 b, the exhaustpipes 5 a and 5 b, and the purge gas supply pipes 6 a, 6 b, 7 a, 7 b and8, respectively, in such a way that a pressure difference can beprovided in a predetermined region, respectively by adjusting theopening rate of each of the valves V1 to V9. However, in FIG. 17, sincethe construction of the apparatus shown in FIG. 17 is substantially thesame as that shown in FIG. 14, except the portions related to thepressure adjustment, only the essential portions of the apparatus areshown.

In the seventh embodiment, control sections (control means) C1 to C9 areprovided for controlling the valves V1 to V9, respectively. Further,pressure detecting sections P1 a and P1 b are provided on the downstreamside (the side of the reaction pipe 2) of the valves V1 and V2 of theprocessing gas supply pipes 3 a and 3 b, respectively. Further, pressuredetecting sections P2 a (P2 b) and P3 a (P3 b) are provided on theupstream side (the side of the reaction pipe 2) and the downstream sideof the valves V3 and V4 of the processing gas supply pipes 5 a and 5 b,respectively. Further, pressure detecting sections P4 and P5 a (P5 b)are provided near the supply port of the purge gas supply pipe 8 in thecylindrical body 4 and a space between the exhaust pipe 5 a (5 b) andthe shutter stand-by chamber 43 a (43 b), respectively. Further,pressure detecting sections P6 a (P6 b) and P7 a (P7 b) are providednear the supply ports of the purge gas supply pipes 6 a (6 b) and 7 a (7b) in the shutter stand-by chambers 43 a and 43 b, respectively.

The control section C1 (C2) inputs the pressure detection value P1 a (P1b) of the pressure detection section P1 a (P1 b) (here, the pressuredetection sections and the pressure detection values are both denoted byuse of the same reference numerals, respectively for convenience ofexplanation) and P4, P6 a, P7 a and P7 b, and controls the opening rateof the valve V1 (V2), in such a way that P1 a (P1 b) becomes larger thanthe maximum value of P4, P6 a, p6 b, P7 a and P7 b, for instance, insuch a way that a pressure difference of 1 to 25 mm can be obtainedbetween the two, for instance. Further, the control section C3 (C4)inputs P2 a (P2 b) and P3 a (P3 b), and controls the opening rate of thevalve V3 (V4) in such a way that P2 a (P2 b) becomes larger than P3 a(P3 b) by 1 to 25 mmHg, for instance.

Further, the control section C5 (C6) inputs P5 a (P5 b) and P6 a (P6 b),and controls the opening rate of the valve V5 (V6) in such a way that P6a (P6 b) becomes larger than P5 a (P5 b) by 1 to 25 mmHg, for instance.Further, the control section C7 (C8) inputs P5 a (P5 b) and P7 a (P7 b),and controls the opening rate of the valve V7 (V8) in such a way that P7a (P7 b) becomes larger than P5 a (P5 b) by 1 to 25 mmHg, for instance.

Further, the control section C9 inputs P4 and P5 a (or P5 b), andcontrols the opening rate of the valve V9 in such a way that P4 becomeslarger than P5 b by 1 to 25 mms, for instance.

The above-mentioned pressure relationship can be summarized as follows:

P1 a (P1 b)>P4 (e.g, when P4 is maximum)

P2 a (P2 b)>P3 a (P3 b)

P6 a (P6 b), P7 a (P7 b), P4>P5 a (P5 b)

In the case where the opening rates of the two valves V3 and V4 arecontrolled in such a way that the pressures on the upstream side of thevalves V3 and V4 of the exhaust pipes 3 a and 3 b are higher than thoseon the downstream side thereof, whenever the wafer W is passed throughthe exhaust ports, even if gas is mixed with the surrounding gas in thenegative pressure region on both the right and reverse surfaces of thewafer W, it is possible to reduce the spread of the gas flow disturbancedue to the gas mixture. As a result, it is possible to reduce theinfluence upon the exhaust gas flow of the exhaust pipes 5 a and 5 b, sothat the backward flow of the gas in the exhaust pipes 5 a and 5 b canbe reduced or prevented

Further, in this embodiment, the pressure is so adjusted that thepressure near the outlet port of the processing gas supply pipe 3 a (3b) is slightly higher than that near the supply ports of the purge gassupply pipes 6 a (6 b) and 7 a (7 b), and further the pressure is soadjusted that the pressure at the region slightly downward side from theexhaust port is higher than that near the supply ports of the purge gassupply pipes 6 a (6 b) and 7 a (7 b) and 8. Therefore, even when thewafer W is being moved upward, it is possible to prevent the processinggas from being mixed with the purge atmosphere or the purge gas frombeing mixed with the processing gas atmosphere. In other words, sinceboth the gases are sucked from each atmosphere into the exhaust pipes 5a and 5 b without disturbance, it is possible to form an oxide film onthe wafer W with a high intra-surface uniformity of the film thickness.

Here, in the seventh embodiment shown in FIG. 17, each pressuredifference is detected between two of the sections, respectively.Therefore, the pressure of each section is detected, to calculate eachpressure difference in each control section. Instead of this, however,it is also possible to use a pressure differential meter and to inputthe obtained pressure difference value to the control means. Further, itis also possible to combine the sixth embodiment shown in FIG. 14 withthe seventh embodiment shown in FIG. 17; that is, to combine the waferspeed control with the pressure control at each section.

USABLE POSSIBILITY IN INDUSTRIAL FIELD

As described above, the heat treatment method and apparatus according tothe present invention can be used suitably when an extremely thin oxidefilm such as a gate oxide film, a capacitor insulating film, etc. isformed on a processed body such as a semiconductor device in accordancewith the oxidization process or the diffusion process of impurity ions.In addition, the present invention can be applied when the CVDprocessing and heating processing such as annealing processing areperformed.

What is claimed is:
 1. An apparatus for heat-treating a processed body,while supplying a processing gas, by use of the apparatus having areaction vessel enclosed by a heating furnace; a shift and mount chamberdisposed on a lower side of the reaction vessel, for shifting andmounting the processed body; a processed body holding member moved upand down between the reaction vessel and the shift and mount chamber,for holding the processed body; and an exhaust passage connected to thereaction vessel, which comprises: a pressure adjusting valve disposed inthe exhaust passage; means for detecting a difference in pressurebetween a reaction vessel side and a downstream side of said pressureadjusting valve in the exhaust passage; and control means forcontrolling opening rate of said pressure adjusting valve in such a waythat the pressure on the reaction vessel side is higher than that on thedownstream side, on the basis of the pressure difference obtained bysaid detecting means.
 2. An apparatus for heat-treating a processedbody, while supplying a processing gas, by use of the apparatus having areaction vessel enclosed by a heating furnace; a shift and mount chamberdisposed on a lower side of the reaction vessel, for shifting andmounting the processed body; a processed body holding member moved upand down between the reaction vessel and the shift and mount chamber,for holding the processed body; a processing gas supply passageconnected to the reaction vessel; an exhaust passage having an exhaustport lower than a supply port of the processing gas supply passageconnected to the reaction vessel; and a purge supply passage having asupply port at a lower side region from the exhaust port communicatingwith the reaction vessel; which comprises: first, second and thirdpressure adjusting valves disposed in the processing gas supply passage,the exhaust passage, and the purge gas passage, respectively; means fordetecting a first difference in pressure between purge gas region and adownstream side of said first pressure adjusting valve in the processinggas supply passage; a second difference in pressure between a reactionvessel side and a downstream side of said second pressure adjustingvalve in the exhaust passage, and a third difference in pressure betweena position near the exhaust port and a position away from the exhaustport of the purge gas region; and control means for controlling openingrate of said first pressure adjusting valve in such a way that pressureon the downstream side is higher than pressure in the purge region,opening rate of said second pressure adjusting valve in such a way thatpressure on the reaction vessel side is higher than pressure on thedownstream side, and opening rate of said third pressure adjusting valvein such a way that pressure at the position away from the exhaust portis higher than pressure at the position near the exhaust port, on thebasis of the first, second and third pressure differences obtained bysaid detecting means, respectively.